What are the allusions in Canto 23?

There is an allusion to Aesop's fable about the frog and the mouse, both of whom perish at the hands of a hawk. Dante makes a parallel between the frog and mouse with he and Virgil, begging the question whether or not they will make it through. 

There is a reference/allusion to Frederick II. Dante observes a group of tired, weeping people with mantles and hoods over their eyes. He says that their attire is...

There is an allusion to Aesop's fable about the frog and the mouse, both of whom perish at the hands of a hawk. Dante makes a parallel between the frog and mouse with he and Virgil, begging the question whether or not they will make it through. 

There is a reference/allusion to Frederick II. Dante observes a group of tired, weeping people with mantles and hoods over their eyes. He says that their attire is bright but heavy with lead underneath. Allegedly, Frederick II (Holy Roman Emperor in the 13th century) would clothe people in lead and have them burned. Dante suggests that their attire was like straw when compared with what these people in Hell are wearing. 

These lead-clad people are "hypocrites" and claim to be Frati Gaudenti, an order of knights under Pope Urban IV, who were accused of hypocrisy: looking out for their own personal gain rather than the greater good. 

Dante then sees Caiaphas, the Jewish High Priest, who is believed to have orchestrated the plan to convict and try Jesus Christ. Here they find Caiaphas crucified with three stakes on the ground.